did he get a concussion? it looks like he stood up, walked and went down again...
No concussion, but he has a massive bruise on his inner thigh/crotch area as well as a swollen (not broken or sprained) wrist. He realized that Bry and Ryan were coming, and knew that if he didn't drag his bike off the middle of the trail, one of them was going to go down HARD. There's too much speed off that step down to be able to stop in time if he left it...